The intervention studies of the Claude D. Pepper Older Americans Independence Center (OAIC) all are centered around the broad theme that losses of axial mobility (mobility of the neck and back) contribute to functional limitations. The investigations have as one of their major hypotheses that improvements in axial mobility will lead to improvements of specific aspects of function. Each investigation includes an exercise intervention component with exercises directed at least in part to axial mobility. One of the OAIC intervention studies and the measurements for a second study are carried out in the GCRC. The first study is a randomized clinical trial comparing exercise to no exercise for participants who are in the early and middle stages of Parkinson's disease (PD). The second is a randomized clinical trial comparing a traditional aerobic conditioning program to an aerobic conditioning program plus an axial mobility exercise program for sedentary community dwelling older individuals.